Explanation:

To configure a common global error handler flow that can be reused across all of an organization’s Mule applications deployed on CloudHub, the best approach is:

✅ C. Create a Mule Plugin project. Create a common-global-error-handler flow inside the plugin project. Use this plugin as a dependency in all Mule applications.

Why a Mule Plugin project: A Mule Plugin project is designed to encapsulate reusable components, such as flows, configurations, or error handlers, that can be shared across multiple Mule applications. By creating a common global error handler flow in a Mule Plugin project, you can package it as a reusable artifact and include it as a dependency in all Mule applications. This promotes modularity, maintainability, and consistency across the organization’s applications.

How it works:
➜ Create a Mule Plugin project using Maven (with the mule-plugin classifier in the pom.xml).
➜ Define the common-global-error-handler flow within this project.
➜ Build and deploy the plugin to a repository (e.g., Anypoint Exchange or a Maven repository).
➜ Add the plugin as a dependency in the pom.xml of each Mule application.
➜ Reference the error handler in the Mule applications using the plugin’s configuration, ensuring consistent error handling across all applications.

Why CloudHub compatibility: CloudHub supports deploying Mule applications with dependencies on Mule Plugins. This approach works seamlessly in CloudHub as the plugin is resolved during deployment, and the error handler flow can be invoked as needed.

❌ Why not the other options?

A. Create a Mule plugin project, create a common-global-error-handler flow inside the plugin project, use this plugin as a dependency in all Mule applications, import that configuration file in Mule applications: This option is incorrect because Mule Plugins do not require importing a configuration file explicitly. Once the plugin is added as a dependency, its components (e.g., flows or error handlers) can be referenced directly in the Mule application without additional imports, making the “import configuration file” step unnecessary and misleading.

B. Create a common-global-error-handler flow in all Mule Applications, refer to it flow-ref wherever needed: This approach is inefficient and violates the principle of reusability. Creating the same error handler flow in every Mule application leads to code duplication, maintenance overhead, and potential inconsistencies across applications. It does not leverage a centralized, reusable component.

D. Create a Mule domain project, create a common-global-error-handler flow inside the domain project, use this domain project as a dependency: Mule Domain projects are used to share resources (e.g., connectors, configurations) across multiple Mule applications deployed on the same runtime instance (e.g., on-premises servers). However, CloudHub does not support Mule Domain projects, as each application runs in its own isolated runtime. Therefore, this approach is not applicable for CloudHub deployments.

Reference:
MuleSoft Documentation: Mule Plugin Development and Anypoint Exchange for Reusable Assets
MuleSoft Documentation: CloudHub Deployment Limitations